This study examines how climate citizens' assemblies (CCAs) influence youth engagement, both in practice and in shaping perceptions of political "voice", drawing on Albert O. Hirschman's "Exit, Voice, and Loyalty" framework. Through qualitative analysis of 71 interviews, participatory workshops, and observational data across four cities—Barcelona, Bologna, Geneva, and Paris—it explores whether CCAs address youth climate activists' demands, enable meaningful participation, and yield policy outcomes aligned with their claims. Findings reveal divergent perceptions: in Bologna, co-design with activists tended to foster trust, while Barcelona saw disillusionment due to unmet expectations. Geneva's embedded deliberative processes strengthened institutional loyalty, whereas Paris faced skepticism as activists turned to civil disobedience. Overall, CCAs' effectiveness hinges on inclusivity, follow-through, and communication; when perceived as tokenistic, they risk reinforcing disengagement ("exit"). The study underscores the need for embedded, responsive democratic innovations to sustain youth participation amid climate crises.